(NaturalNews) On May 1, a worker at Japan’s crippled Fukushima Daiichi nuclear power plant discovered a storage tank leaking radioactive water, plant operator Tokyo Electric Power Company (TEPCO) announced the following day.

In March 2011, a major earthquake and tsunami triggered three separate meltdowns at the Fukushima plant. Large quantities of water have been rendered radioactive from being used to cool the crippled reactors. In addition, groundwater has been leaking into the basements of the reactors, mixing with contaminated water there and also becoming radioactive. TEPCO has been frantically pumping this water out and concentrating it into onsite storage tanks in an effort to minimize how much radioactive water spreads beyond the plant as groundwater.

The leak was found on the same day that TEPCO resumed tests for its beleaguered plans to construct a nearly mile-long “ice wall” of frozen soil to prevent more groundwater from infiltrating into the plant.

Second leak in weeks
The leaking tank was discovered when the worker noticed a wet patch just three inches wide next to it. The ground at that spot tested at 70 microsieverts per hour of beta-ray-emitting radioactivity; this is more than 600 times the 0.11 microsieverts per hour of maximum recommended exposure.

Workers piled sandbags around the tank to keep the leak from spreading, TEPCO said.

The leak was the second one reported in the last few weeks. In late April, a still-unexplained power outage caused water transfer pumps at the plant to shut down. The pumps were being used to move radioactive water from one drainage channel into another after it was revealed that water had been spilling from the first channel directly into the Pacific Ocean. When the power to the plants shut down, radioactive water resumed flowing into the sea. Approximately 100 tons of contaminated water — also exceeding the legal limit — are estimated to have escaped before power was re-established.